Research On Large Amplitude Periodic Orbits And Control Of Bistable Piezoelectric Energy Harvester

Piezoelectric materials can generate electrical charges when strained,which permits to effectively collecte vibration energy by attaching a piezoelectric wafer to a vibration cantilever beam.The amplitude of vibration of the cantilever beam certainly affects the output voltage of the energy harvester since amount of charge generated by the piezoelectric material is proportional to the strain produced.A bistable piezoelectric energy harvester can exhibit small amplitude periodic motion within the potential well,chaotic motion between potential wells,and large amplitude periodic motion between potential wells at different external excitation.It is obvious that the energy harvester can generate a relatively larger periodic voltage only when the bistable piezoelectric energy harvester is in the orbit of a large amplitude periodic motion.Therefore,it is a reliable method for increasing the output voltage by controlling the energy harvester to work in such orbit.It is well known what kind of the motion the bistable piezoelectric energy harvester will take is dependent upon the initial condition when the external excitation is firmly determined.For the aim of making the energy harvester work in a large amplitude periodic orbit with any initial condition,a controller should be simulated which will consum some amount of energy.In this thesis,the bistable cantilever piezoelectric energy harvester is taken as the research objects.And the dynamic characteristics and efficiency of the energy harvesters under different external excitation and initial conditions are analyzed.The intermittent control method is applied to control the bistable piezoelectric working in a large amplitude periodic orbit.The influence of controller parameters on the energy consumption of the controller was analyzed and the control parameters were optimized.The main research work and conclusions of this thesis are as follows:1.Using the 0-1 chaos test method,the motion of bistable piezoelectric energy harvester is systematically analyzed with different external excitation and different initial conditions.The efficiency of the bistable piezoelectric energy harvester working in different orbit is also analyzed.The results show that under the different amplitudes of external excitation,the bistable energy harvester can present small amplitude periodic motion in the well,chaotic motion between the wells,and large amplitude periodic motion between the wells.In the case when external excitation is determined,the energy harvester can also work in a large amplitude periodic orbit by adjusting the initial conditions.By comparison,it is found that efficiency of the bistable piezoelectric energy harvester working in the large amplirude periodic orbit is superior to that of working in the chaotic motion orbit between the well,which is better than that of working in the periodic motion in the well.2.With Simulink,the simulation model of bistable piezoelectric energy harvesting control system is established.The contrained intermittent control method is employed to control the bistable piezoelectric energy harvester from small amplitude intrawell periodic orbits or interwell chaotic orbit to large amplitude interwell periodic orbits.The results show that the controller consumes limited energy while leading the bistable energy harvester to working in a large amplitude period orbit.3.The energy consumption of the controller during the controlling is studied.The index of energy consumption is introduced.The impact of controlling parameters on the indes is analyzed.The genetic algorithm is used to optimize the control parameters,and the numerical simulation of the optimized control parameters is carried out.The results show that the parameters of controller have a certain influence on the energy consumption of the controller.The controller with optimized parameters will reduce the energy consumption and enhance the efficiency of the energy harvester.